VACAVILLE -- His voice trembling with emotion, slain California Highway Patrol Officer Kenyon Youngstrom's beat partner told an audience of thousands at a memorial service Thursday that he sought solace in faith after seeing his "brother" shot in the line of duty last week.

"I often have thoughts that creep into my mind of 'Why?' or 'What if?' or 'I could have,'" said CHP Officer Tyler Carlton, who was performing a traffic stop on Interstate 680 in Alamo on Sept. 4 when the suspect he had pulled over suddenly shot Youngstrom. "But then I remind myself that everything does happen for a reason, that this was all in God's plan, and that his plans are perfect every time."

Carlton's voice broke as he read scripture and then bid farewell to Youngstrom, who died after being taken off life support the next day.

"Ken, I know you can hear me," said Carlton, who fatally shot the motorist who killed Youngstrom. "I want to thank you from the bottom of my heart for always being there for me. And I look forward to seeing you again, brother."

Youngstrom's family was joined by friends, thousands of law enforcement officers from all over California and across the United States, and ordinary people touched by Youngstrom's courage and sacrifice as a memorial for the seven-year CHP veteran Thursday morning.

The two-hour service at The Mission church in Vacaville was sorrowful, but as Youngstrom's loved ones and colleagues spoke about his irrepressible personality, smiles and laughter filled the sanctuary.

"He loved us a lot," said Youngstrom's teenage son, Alex, "but what I think he loved even more was making people smile. It was like his hobby.

"When I hear stories about how much he would talk about us (his children), it really touches me," Alex Youngstrom added. "I'm really proud of my dad."

Addressing the CHP officers who packed the church, the 17-year-old said, "My dad loved all of you guys, and I can see that you loved him."

The funeral procession, escorted by dozens of CHP motorcycles and patrol cars, left a mortuary in St. Helena about 7:30 a.m. Thursday. The hearse carrying Youngstrom's casket passed through a towering gateway at the church, with two fire engines holding a giant American flag aloft, at 9 a.m.

Officers from law enforcement agencies as far away as Alaska, Minnesota, Missouri and West Virginia attended the service. Scores of officers stood at attention, saluting, at the 10 a.m. start of the service, as two minutes of silence gave way to the sound of a lone bagpipe player, who led the processional that brought the slain officer's body into the church.

They stood and saluted again at the conclusion, as the officer's body was taken to a private interment ceremony.

Gov. Jerry Brown and state Attorney General Kamala Harris were among the approximately 3,000 people attending the service.

CHP Commissioner Joe Farrow said Youngstrom made the ultimate sacrifice.

"The freedoms we all enjoy as Americans come with a cost," Farrow said. "Sometimes that cost is high. Sometimes it is devastating."

"It takes a special person to wear the CHP badge, and your dad was one of the best," Farrow told the officer's children. "After Kenyon took the oath and donned his uniform, he never swerved from the path of duty."

He added, to Youngstrom's wife: "We are thankful that Kenyon was surrounded by his family and their love during his final moments."

Farrow was followed by CHP Division Chief Teresa Becher, who told the gathering, "I've never known how my heart could be so broken and so full at the same time."

Youngstrom, 37, had the ability to make everyone feel comfortable, his fellow officers said.

"He just had the friendliest face," retired CHP Captain Jim Cahoon told a sea of uniforms and family and friends at the church.

"As much as he was trying not to smile, it was just exuding out of him. Right off the bat, I had a comfortable feeling, a welcoming feeling. Anyone that had ever known him knows exactly what I am talking about."

The officer's niece, Storm Youngstrom, spoke not only of her uncle's playful, fun nature, but his personal inspiration to her.

"I know Uncle Ken is watching from above. I know he's proud of everything everyone's done for him," Storm Youngstrom said. "Kenyon turned out to be the best man anyone could have hoped for.

"To me, he wasn't only my uncle. He was a hero, and he was a father to me. I can't wait to start my future and join the academy and take after Kenyon."

Youngstrom, a Cordelia resident, was the 223rd CHP officer to be killed in the line of duty since 1929.

After the shooting, colleagues from the CHP maintained an around-the-clock vigil at John Muir Medical Center in Walnut Creek until Youngstrom was taken off life support.

Because he was a registered organ donor, Youngstrom's liver, pancreas, kidneys and heart were given to four waiting patients, according to the California Donor Transplant Network. Those donors included a 29-year-old mother and a 50-year-old married father of four.

After graduating from the CHP Academy in February 2006, Youngstrom was assigned to the CHP's Contra Costa office in Martinez. He transferred to the Golden Gate Division headquarters in Vallejo in 2009, and had transferred back to the Contra Costa office on Aug. 1.

Before joining the CHP, Youngstrom had served with the U.S. Army Reserve from 1994 to 2002, attaining the rank of specialist.

Youngstrom is survived by his wife, Karen, his two sons and two daughters, his parents, Gaylord and Jill Youngstrom, of Riverside, four brothers and a sister.

Two Bay Area banks have set up accounts to benefit Youngstrom's family:

At any Mechanics Bank branch, mention the officer's name to the teller and direct that funds be contributed to the trust account in his name. Checks payable to "For Benefit of Officer Kenyon Youngstrom" can also be mailed to Mechanics Bank, 1350 N. Main St., Walnut Creek, Calif., 94596. Wire transfers can be sent to routing number 121102036 and addressed "For Officer Kenyon Youngstrom."